Strings/Task7

//Write a program that encodes and decodes a string using given encryption key (cipher). The key consists of a sequence of characters. The encoding/decoding is done by performing XOR (exclusive or) operation over the first letter of the string with the first of the key, the second – with the second, etc. When the last key character is reached, the next is the first.

using System;
using System.Text;

class StringEncoding
{
    static string EncodeString(string str, string key)
    {
        var result = new StringBuilder();
        int index = 0;
        for (int i = 0; i < str.Length; i++)
        {
            result.Append((char)(str[i] ^ key[index]));
            if (index + 1 < key.Length)
            {
                index++;
            }
            else
            {
                index = 0;
            }
        }

        return result.ToString();
    }
    static string DecodeString(string str, string key)
    {
        return EncodeString(str, key);
    }

    static void Main()
    {
        Console.Write("Enter a text: ");
        string text = Console.ReadLine();

        Console.Write("Enter a chiper: ");
        string cipher = Console.ReadLine();

        string encText = EncodeString(text, cipher);
        Console.WriteLine("After encoding: " + encText);

        string decText = DecodeString(encText, cipher); //Decoding is the same as encoding because if a^b = c --> a = c^b
        Console.WriteLine("After decoding: " + decText);

    }
}